Deleting Groups from Contacts

Delete contacts or contact groups in Contacts on Mac

You can delete contacts and groups at any time.

In the Contacts app  on your Mac, do any of the following:

• Delete a contact: Select a contact, then press the Delete key.
• If you select a contact who belongs to a group, click Delete in the message that appears.
• Delete a group: Select a group in the sidebar, then press the Delete key.
• If a group is used in a Smart Group (by including a condition that uses “Card is member of” or “Card is not member of”), you can’t delete the group until you change the condition or delete the Smart Group.

You can’t delete contacts in read-only accounts such as Google and Yahoo!; you must delete the contacts directly in Google or Yahoo!, for example. If you don’t want to see contacts from a specific account, stop using the account in Contacts. To do so, choose Contacts > Accounts, select the account, then deselect its Contacts checkbox.

If you stop using or remove an account, any edited contacts remain in your default contacts account.

https://support.apple.com/guide/contacts/delete-contacts-or-contact-groups-adrb1f6bae26/mac

If you mean you want to delete the entry that pops up when you start typing in the "To:" field, no, you most likely can't delete it. However, over time not using it, it will be overwritten.

Great news Prudence, you're welcome & good luck. :)